Electrical components which are used to establish various circuit contacts should have a low, stable contact resistance, which can be assured only if the contact metal is a good conductor and does not substantially deteriorate with time. Noble metals, such as gold and the metals of the platinum family can be used to protect electrical contacts from corrosion and at the same time provide solderability properties and low electrical contact resistance at low loads. Such coatings have relatively low chemical reactivity and are resistant to oxidation. However, such coatings are extremely expensive.
Low-cost substitutes for such coatings have been suggested. One particularly good example is a palladium-nickel alloy. Such can be deposited in accordance with the method disclosed in U.S. Pat. No. 4,100,039 to Caricchio, Jr., et al. Although, the process disclosed in U.S. Pat. No. 4,100,039 is quite adequate, such does suffer from a few disadvantages. In particular, the amount of palladium in the deposited alloy tends to change more than desired upon use and aging of the bath. Also, in order to obtain a coating having a uniform satin bright appearance, a sulfite ion is included in the compositions disclosed in U.S. Pat. No. 4,100,039. Moreover, obtaining higher nickel concentrations in coatings made pursuant to the method disclosed in U.S. Pat. No. 4,100,039 is quite difficult.